Dielectrophoretic transport increases depth of penetration of fluoride into enamel

Objectives: To explore, in a pilot study, the optimal conditions for an innovative dielectrophoretic (DEP) technique to deliver fluoride into tooth enamel. DEP uses a nonuniform electrical field with two alternating current frequencies to polarize (orient) and motivate particles. Methods: Acidulated phosphate fluoride gel (APF) was applied to bovine tooth enamel with DEP or without (passive diffusion, PD). Three (DEP) conditions were tested: 20-minutes with 5000 & 10 Hz (DEP20); 40-minutes with 5000 & 10 Hz (DEP40); 20-minutes with 5000 & 10 Hz followed by 20-minutes 400 & 10 Hz without APF gel (DEP2x). Passive diffusion time was 20-minutes. Treated teeth were cross-sectioned and fluoride concentrations at various depths from the enamel surface were analyzed using wavelength dispersive spectrometry. Baseline fluoride concentrations were determined with electron probe microanalysis at areas that had been protected by nail polish. Results were analyzed by ANOVA/Student-Newman-Keuls post hoc (p=0.05). Results: Mean (standard deviation) fluoride concentrations are shown in the table below. Concentrations in the diffusion group were higher than the baseline at 10-20 ìm depths, but not significantly; all DEP-groups were significantly higher at those depths. Significantly higher fluoride concentration was found at 50 ìm depth in the DEP2x group. Conclusion: A high-frequency (5000 & 10 Hz) followed by low-frequency (400 & 10 Hz) DEP was the optimal condition. DEP enhanced fluoride delivery through tooth enamel, reaching higher concentrations and penetration depths than the diffusion process. Acknowledgments: Supported by the University of Tennessee Dental Alumni Research Grant.